Chlamydophila pneumoniae is an obligate intracellular bacterium and is known to be a common cause of community-acquired pneumonia (CAP). While pneumoniae and bronchitis are most commonly associated with C. pneumoniae infections, other possible illnesses include pharyngitis, laryngitis, sinusitis and otitis. Most cases of pneumonia are relatively mild, but C. pneumoniae can cause severe disease requiring hospitalization. In the United States alone, there are approximately 50,000 pneumonia-related hospitalizations a year which are caused by a C. pneumoniae infection. Humans are the only known reservoir of this organism, and transmission is person-to-person by respiratory secretions.
A number of studies have also demonstrated an epidemiological link between C. pneumoniae infection and atherosclerosis. Although it has been shown that C. pneumoniae has the capacity to infect smooth muscle cells found within atherosclerotic lesions, it is still not known what role the organism plays in the pathogenesis of atherosclerosis. Associations with Alzheimer's disease, asthma and reactive arthritis have also been proposed.
Presently, there are no standardized diagnostic methods for detecting C. pneumoniae infections, and means for performing rapid diagnosis are not readily accessible. Diagnostic techniques which have been employed include serologic antibody tests, cell culture, antigen detection and PCR-based nucleic acid amplification assays. The most commonly used serologic assay is the microimmuno-fluorescent (MIF) test but it requires significant skill to evaluate appropriate fluorescence, has not been well standardized, and may be less reliable in the serodiagnosis of children than adults. Culture is difficult because the organism is fastidious and takes considerable time to grow. Antigen detection is relatively insensitive and has been shown to have substantial cross-reactivity with other chlamydias. PCR systems for detecting C. pneumoniae have considerable problems with contamination, inhibitors, specificity and assay complexity. Consequently, most pneumonia diagnoses are made empirically, and the prescribed treatment is generally a B-lactam antibiotic for targeting Streptococcus pneumoniae. While the majority of pneumonias respond to B-lactam antibiotics, atypical pneumonias like C. pneumoniae do not, instead requiring treatment with macrolide. As a result, empirical diagnosis can lead to inappropriate antibiotic treatments with increased drug resistance and health care costs, as well as disease progression. Thus, a need exists for a sensitive and specific test for rapidly diagnosing C. pneumoniae infections.